Hydraulic means for generating signals representative of fluctuating compression forces in railway vehicles and the like



Oct. 7, 1969 s. R. BJEREUS $470,

HYDRAULIC MEANS FOR GENERATING SIGNALS REPRESENTATIVE OF FLUCTUATING COMPRESSION FORCES TN RAILWAY VEHICLES AND THE LIKE 3 Sheets-Sheet 1 Filed March 26. 1968 34 31 33 L 27 H 2 54 F191 41 x 30 INVENTOR van narex-tug BYaawQ'av w ATTORNEY Oct. 7, 1969 s. R. BJEREUS 3,470,696

HYDRAULIC MEANS FOR GENERATING SIGNALS REPRESENTATIVE OF FLUCTUATING COMPRESSION FORCES IN RAILWAY VEHICLES AND THE LIKE 3 Sheets-Sheet 2 Filed March 26. 1968 INVENTOR Sven RQfiw-w- Bjereug BYW @nwwvu ATTORNEY QM, 7, 1969 5, BJEREUS 3,470,696

HYDRAULIC MEANS FOR GENERATING SIGNALS REPRESENTATIVE OF FLUCTUATING COMPRESSION FORCES IN RAILWAY VEHICLES AND THE LIKE 3 Sheets-Sheet 5 Filed March 26, 1968 INVENTOR S Qaqnav- BkrcuS ATTORNEY United States Patent 3,470,696 HYDRAULIC MEANS FOR GENERATING SIGNALS REPRESENTATIVE OF FLUCTUATING COM- PRESSION FORCES IN RAILWAY VEHICLES AND THE LIKE Sven R. Bjereus, Malmo, Sweden, assignor to Svenska Aktiebolaget Bromsregulator, Malmo, Sweden Filed Mar. 26, 1968, Ser. No. 716,018 Claims priority, application Great Britain, Apr. 6, 1967, 15,749/ 67 Int. Cl. F15b 7/00; B61f /00 US. Cl. 6054.5 12 Claims ABSTRACT OF THE DISCLOSURE Hydraulically operated apparatus is provided for converting forces such as those developed in railway vehicle springs into representative signals for actuating responsive devices. The signals are processed in the hydraulic apparatus to provide mean values. Structure is provided for retaining hydraulic fluid in active position after long periods of idleness by circulating the fluid during operation periods. Hydraulic amplification of signal magnitude is attained by a dual piston structure converting small changes in position represented in railway vehicle spring compression into large changes in position of a mechanical member. One embodiment provides output signals in the form of changes of pressure.

This invention relates to apparatus for generating signals derived from fluctuating compression forces, such as operating upon vehicle springs, and more particularly, to signals representing the mean value of a compression force which fluctuates and also varies in mean value.

In certain applications such as in railway vehicles, equipment may become idle for long periods of time before reuse and is subject to inspection and repair at infrequent intervals. Thus, the problem of equipment reliability is presented, particularly in the use of hydraulic equipment with movable pistons where there is a tendency toward leakage of fluids particularly if they are kept under pressure during long periods of time.

Apparatus of the general type afforded by this invention comprises a housing with a main piston slidable therein to a position determined by the force upon the position as opposed to pressure within a main pressure chamber filled with a liquid under a pressure which varies with the compression force. A throttling passage is provided to permit liquid to pass between the main pressure chamber and a secondary pressure chamber including a counter-loaded secondary piston with an effective area smaller than the effective area of the main piston being subject to the pressure of the liquid in the secondary pressure chamber to move the secondary piston and produce signals dependent upon the mean value of the compression force upon the main piston.

Apparatus of this kind is useful for generating signals dependent upon the mean value of the compression force acting on a railway vehicle axle box spring, as this compression force fluctuates as the vehicle is running and also varies in mean value according to the loading and other influences which may affect the vehicle as it is running or stationary.

The signals derived from the motions of the secondary piston, may be transmitted mechanically, hydraulically or electrically or in any suitable manner to one or more responsive devices, such as indicating and/or recording devices or devices for adjusting the leverage ratios in vehicle brake riggings.

Hitherto in hydraulic apparatus of the kind referred to it has been usual to employ hermetically-sealed dia- 3,470,696 Patented Oct. 7, 1969 ice phragms to prevent leakage of liquid. However, prior art apparatus of this type cannot always safely be used in cases where inspection occurs irregularly or after long intervals, and false signals due to leakage could have very detrimental consequences.

The invention is therefore intended to provide improved apparatus of the kind referred to.

According to the present invention apparatus of the kind referred to include pumping means by which liquid is pumped into the main pressure chamber continually as the apparatus is subject to fluctuating compression force and an escape valve which is actuated by the said main piston to control the escape of liquid from the main pressure chamber. In a preferred embodiment the pumping means pumps the liquid from a sump and there are passages and spaces whereby any liquid which passes through the escape valve or leaks past the main or secondary pistons is returned to the sump. Further features and advantages of the invention appear from the following description.

The invention is illustrated by way of an embodiment shown in the accompanying drawings, in which:

FIGURE 1 is a view in vertical section along the line 11 in FIGURE 2 of apparatus embodying the invention;

FIGURE 2 is a plan view of the apparatus shown in FIGURE 1;

FIGURE 3 is a view partially in vertical section through parts of an axle box and a bogie frame of a railway vehicle showing an apparatus according to FIG- URES 1 and 2 being used for generating signals dependent upon the mean value of the force compressing and being transmitted by the axle box springs;

FIGURE 4 is a view in vertical section on a larger scale of a valve forming a part of the apparatus shown in FIGURE 1; and

FIGURE 5 is a view in vertical section of another embodiment of the invention.

The apparatus shown in FIGURES 1 and 2 comprises a housing 1 provided with a bottom cover 2 rigidly secured to the housing 1 by a plurality of bolts 3. A sealing ring 4 is clamped between said housing 1 and cover 2. A main piston 5 is mounted slidably in a cylindrical bore 6 in the housing 1, and a top cover 7 is rigidly secured by siX bolts 8 to the main piston 5.

FIGURE 3 illustrates the disposition of the apparatus on a railway vehicle and shows how the bottom cover 2 may be engaged by axle box springs 9' and 10 resting on an axle box 11 while the main piston 5 bears against a part of a bogie frame 12.

Reverting to FIGURE 1, a sealing ring 13 provides a seal between the main piston 5 and the bore 6 in the housing 1. The movements of the main piston 5 relative to the housing 1 will determine the actuation of an escape valve 14 shown in FIGURE 4 as further described below.

The housing 1 and the main piston 5 define a main pressure chamber in the form of a cavity 65 Wholly filled with liquid medium for transmitting the forces between the main piston 5 and the housing 1 (FIGURE 1), and thus transmits the forces between the axle box 11 and the bogie frame 12 compressing the springs 9 and 10 (FIGURE 3).

The main piston 5 (FIGURE 1) is provided with a cylindrical bore 15 containing a movable secondary piston 16. The bore 15 is the interior cylindrical surface of a sleeve 17 pressed into a correspondingly-shaped space in the main piston 5. The sleeve 17 retains sealing ring 18. A bottom cover 19 is fastened to the main piston 5 by means of screws 20, and a sleeve 21 is rigidly secured to said cover 19. A pin 22 is secured in the bore of the sleeve 21 so as to provide a restricted throttling passage for liquid to pass between the main pressure chamber,

i.e. the cavity 65, and a secondary pressure chamber in the form of a cavity in and under the secondary piston 16 and partially bounded by the sleeve 17 and bottom cover 19.

The secondary piston 16 is counter-loaded, being pressed downwardly by a compression spring 23 action On a spring support 24 resting on the piston 16, with spring 23 bearing at its upper end against an abutment constituted by the top cover 7 which is in fixed relationship to the main piston 5. The piston 16 is provided with an upwardlyextending connecting rod 25 adapted to be connected to a Bowden-cable or other movement-transmitting means leading to one or more responsive devices (not shown). Thus, the motions of the secondary piston 16 and rod 25 are used as signals to which the responsive device or devices respond. Owing to the throttling passage through the sleeve 21 the motions of the piston 16 depend upon the mean value of the force compressing the springs 9 and 10 (FIGURE 3) as further explained below.

The bottom wall of the housing 1 is provided with a bore 26 in which a reciprocating pump piston 27 is slidably mounted. A sealing ring 28 is provided between the said piston 27 and the bore 26, and is retained by a disc 29. The piston 27 is acted upon and moved downwardly by the pressure of the liquid in the cavity 65 above the piston 27 and is forced upwardly by a compression spring 30 bearing at its upper end against a spring support 31 on the piston 27 and at its lower end on a spring support 32 which in turn rests on a shoulder on a stationary pipe 33. The pipe 33 extends into a central bore in the piston 27. A ball 34 rests on the upper end of the pipe 33 so as to form a non-return valve. Another ball 35 is placed in the bore of the piston 27 above said first ball 34 so as to form another non-return valve together with a shoulder 36 acting as a valve seat. A spring locking ring 37 mounted in the bore in the piston 27 prevents the balls 34 and 35 from leaving the bore in the piston 27. In the piston shown in FIGURE 1 the spring 30 is compressed so that its force equals the force exerted on the upper side of the piston 27 when the railway vehicle is empty.

A strong dished spring washer 38 is mounted between the main piston and the cover 19. This spring washer 38 is normally not exposed to any forces, but if there is a lack of insutficiency of liquid under the main piston 5 in the cavity 65 for some reason the said spring washer 38 will transmit forces between the main piston 5 and the housing 1. During the running of the railway vehicle the main piston 5 will reciprocate even if supported on the housing 1 only by the spring washer 38.

The apparatus as described so far will function as follows:

The pressure of the liquid enclosed in the main pressure chamber or cavity 65 by the main piston 5 and the housing 1 is proportional to the force transmitted between said piston 5 and said housing 1. However, as the force thus transmitted does vary substantially during the running of the railway vehicle the pressure of the liquid in the cavity 65 will vary accordingly. The pressure of the liquid acting on the secondary piston 16 is opposed by the spring 23, but in order to move the secondary piston 16 influencing the said spring 23 the liquid has to pass the restricted annular throttling passage between the sleeve 21 and the pin 22. Thus, rapid fluctuations or variations in pressure of short duration will have little or no influence on the position of the connecting rod 25 whereas variations in the mean value of the compression force will cause liquid to flow through the said throttling passage with consequent motions of the secondary piston 16 and the connecting rod 25.

During operation some leakages of liquid are impossible to avoid. Even if the leakages are kept very small, it should be remembered that an apparatus on a railway vehicle may be left without inspection for several years. The apparatus is therefore provided with passages and 4 spaces whereby any liquid which passes through the escape valve 14 or other leaking liquid will be returned to and accumulated in a sump formed by the bottom cover 2. Thus, liquid passing the sealing ring 18 will flow over the top of the piston 5 and through a radial bore leading to an annular chamber 39 in the housing 1. Advantageously, the piston 5 may be provided with an annular recess covered by a dirt-excluding lid (not shown) which is clamped between the cover 7 and the piston 5. Liquid leaking past the sealing ring 13 will also pass to the said annular chamber 39. The said chamber 39 is in turn drained by a channel 40 leading to a space 62 between the housing 1 and the bottom cover. From there the liquid flows through channels 63 into a sump 64 in the bottom cover 2.

Variations in the pressure of the force-transmitting liquid in the main pressure chamber or cavity 65 will cause a reciprocating movement of the pump piston 27. An increase in the said pressure will cause a downward movement of the piston 27. Even the piston 5 will be moved downwards relative to the housing 1, although only through a small distance compared with the movement of the piston 27. The ball 34 together with the pipe 33 will act as a piston forcing some of the liquid between the balls 34 and 35 to pass upwards through the valve consisting of the ball 35 and its valve seat 36. Consequently, the amount of liquid in the cavity 65 enclosed by the housing 1 and the piston 5 will increase each time the piston 27 is forced downwardly. During an upward movement of the piston 27 caused by the spring 30 when there is a decrease in pressure of liquid above said piston 27 the distance between the valve balls 34 and 35 will increase and reduced pressure will occur in the space between them. Such reduced pressure will suck up liquid from the sump 64 through a transversallyarranged passage 41 at the bottom of the fixed pipe 33.

If the railway vehicle has been stationary for such a long period that there is no pressure in the cavity 65 and the dished spring Washer 38 is transmitting all the forces between the main piston 5 and the housing 1, this state being caused by leakage of liquid, the pumping of liquid from the sump 64 will immediately start as the vehicle starts running because the spring washer 38 will allow a relative movement of the housing 1 and the piston 5. At the first upward movement of the piston 5 relative to the housing 1 reduced pressure will occur in the cavity 65 and liquid will be sucked up into the cavity 65, passing both of the non-return valves 34 and 35. When a converse relative movement starts the valve 34 will be closed and a pressure is built up in the cavity 65, sooner or later causing the piston 27 to move downwards.

The escape valve 14 is arranged to provide an escape or overflow as soon as the main piston 5 is elevated above a certain height relative to the housing 1. During running of the vehicle liquid is constantly being pumped from the sump 64 into the cavity 65 under the main piston 5, and the valve 14 ensures that the surplus of liquid is returned to the sump 64.

As shown in FIGURE 4, the valve 14 comprises a hollow plug 42 screwed into a hole in the bottom of the housing 1. A hollow piston 43 is movable in a bore 44 in the plug 42 and is urged upwardly by a compression spring 45. The spring 45 bears against a shoulder on a valve stem 46 provided with a conical valve surface for blocking a hole 47 in the plug 42. The valve stem 46 has a collar 46 engaging an inwardly-extending shoulder 48 in the hollow piston 43 and is forced towards this position by a compression spring 49 which is stronger than the spring 45. Liquid is allowed to pass between the piston 43 and the bore 44 in the plug 42.

It will be understood that the piston 43 will always tend to move upwards but its travel in this direction is limited by contacting the main piston 5 (FIGURE 1). The piston 43 may be depressed beyond the position shown in FIGURE 4 without causing damage to the valve stem 46. However, if the main piston 5 is elevated sufficiently, the spring 45 lifts the piston 43 beyond the position of FIGURE 4 and the valve stem 46 is removed from the hole 47 and liquid will escape to the space 62 (FIGURE 1) and flow to the sump 64.

The apparatus shown in FIGURE 5 is in many ways similar to that described with reference to FIGURES 1 to 4, and thus only the differences will be explained in detail. The housing 1, the main piston 5, the cover 2, and the piston together with the adjacent parts all function in a manner somewhat similar to the corresponding details shown in FIGURES 1 to 4. Thus, the force between the housing 1 and the main piston 5 is transmitted through a liquid and the pressure of the liquid transmitted through a throttling passage moves a secondary piston 16 movably arranged in the main piston 5.

However, the piston 16 shown in FIGURE 5 is not counterloaded by a spring force but is acted upon by a flexible membrane 50 via a cup-shaped member 51. The upper side of the flexible membrane 56 is exposed to the pressure of compressed air fed through a bore 52 in the top cover 7 and passed to another bore 53. The flow of compressed air is governed by an air valve centrally disposed in the cover 7. The said air valve comprises a valve stem 54 rigidly mounted on the cupshaped member 51. The valve stem 54 is adapted to engage a valve member 55 provided with a central bore 56. The valve member 55 is urged downwardly by a compression spring 57, and the downward movement is limited by a valve seat on a valve insert 58 mounted in a bore in the top cover 7. A flexible membrane 59 is clamped between the valve insert 58 and another insert member 60. The latter insert member 69 is provided with bores 61 forming free passages between the outer atmosphere and the central bore 56 in the valve member 55.

The apparatus shown in FIGURE 5 will function as follows:

The pressure of the compressed air above the membrane 50 is a direct function of the force transmitted between the housing 1 and the main piston 5. Thus, the bore 53 may be connected by one or more pipes to one or more pressure-responsive devices, for example to pressure gauges or to any pressure registration apparatus which may be used for direct reading or recording of the mean value of the compression force transmitted through the apparatus.

If the transmitted force increases, the piston 16 will move upwards relative to the main piston 5 and such movement will cause the valve stem 54 to lift the valve member 55. Compressed air from the bore 52 will now be fed to the space above the membrane 50 and the air pressure in said space will increase, thus causing a downwardly-directed movement of the cup-shaped member 51 and thus of the valve stem 54. This movement will continue until the valve member 55 engages the valve seat of the insert 58 and further supply of compressed air is cut off.

If the transmitted force is decreased, the piston 16 and thus the valve stem 54 will move downwards from the position shown. The valve member 55 will remain engaged with the valve seat of the insert 58 but now compressed air above the membrane 51 may escape through the passages 56 and 61. This will continue until the pressure above the membrane 50 has decreased so much that the piston 16 is moved up again to establish contact between the valve stem 54- and the valve member 55 and thus close the passage by means of the bore 56. In this way the motions of the secondary piston 16 are used as signals transmitted pneumatically to the said pressure-responsive device or devices.

Having therefore described the invention by means of different embodiments with their construction and operation, those features of novelty believed descriptive of the spirit and nature of the invention are defined with particularity in the appended claims.

What is claimed is:

1. Hydraulic apparatus for converting fluctuating compression forces into signal variations comprising hydraulic means including a pressure chamber with hydraulic fluid and means to establish pressure upon said fluid in proportion to said compression forces, signal conveying means actuated by said hydraulic means, and circulation means including a hydraulic fluid reservoir and pumping means responsive to fluctuations of said compression forces for circulating hydraulic fluid from said reservoir through said chamber.

2. Apparatus as defined in claim 1, including an escape valve in said pressure chamber actuated at a predetermined position to pass fluid, and a conveyance passage to pass fluid from said chamber to said reservoir through said valve.

3. Apparatus as defined in claim 1, including hydraulic piston means communicating with said pressure chamher, and a conveyance passage to pass fluid leaking by said piston means to said reservoir.

4. Apparatus as defined in claim 1, wherein the hydraulic means includes a main piston and a secondary piston, means conveying said compression forces to said main piston, and means deriving said signal variations from said secondary piston.

5. Apparatus as defined in claim 4, wherein said secondary piston is movably confined in said main piston.

6. Apparatus as defined in claim 4', including a fluid passageway between said pistons and means in said fluid passageway establishing a mean value of changes in said secondary piston for compression forces upon said main piston.

7. Apparatus as defined in claim 4, wherein the secondary piston is loaded by spring means to establish a force countering compression variations on said main piston.

8. Apparatus as defined in claim 4 for operation with a responsive device including mechanically movable means for coupling said secondary piston to said responsive device.

9. Apparatus as defined in claim 4 for operation with a responsive device including a source of compressed air and means coupled to said secondary piston to control the pressure of air from said source to operate therewith said responsive device.

14). Apparatus as defined in claim 1, wherein said pumping means comprises a reciprocating pump piston, means moving the pump piston in one direction with rising pressure in said chamber and spring biasing means for moving the pump piston in the opposite direction.

11. Apparatus as defined in claim 1, wherein said pumping means comprises a reciprocating pump piston, and including a fluid flow passageway through said piston with two non-return valves therein governing fluid flow therethrough.

12. Apparatus as defined in claim 1, wherein a piston is actuated by said fluid and spring means is located within said pressure chamber to engage and oppose the piston when fluid in said pressure chamber decreases below a predetermined quantity.

References Cited UNITED STATES PATENTS 1,337,501 4/1920 Arluskes 280106.5

MARTIN P. SCHWADRON, Primary Examiner R. B. BUNEVICH, Assistant Examiner US. Cl. X.R. 

